conversion from NED to ENU for vectornav imu

asked 2018-06-14 02:08:48 -0500

Marek
18 ●1 ●2 ●2

Hello, I have a vectornav 200 IMU for which i am using the driver provided here: https://github.com/dawonn/vectornav

I wasn't able to find a clear answer on how to prepare the IMU to be used in EKF node. Apparently the IMU is publishing its orientation in NED frame. In case I would like to use the IMU with no translation and rotation wrt base_link,

1 How should the actual device be placed?

2 What should be the static transform wrt base_link?

3 How to make imu publish in ENU frame?

I have used the setup proposed here: https://github.com/ros-perception/imu... but so far I wasnt able to get the right result. Thanks!

answered 2018-06-14 02:46:01 -0500

mpc_agro
26 ●2 ●3 ●4

You are asking a very broad question, with few details. Since this is an IMU with GNSS (GPS), I assume you are doing an outdoor project.

I personally did a project with an vectornav 200 IMU in ROS: https://youtu.be/rzTScFbkdG0 https://vision.eng.au.dk/uav_lidar/ http://www.mdpi.com/1424-8220/17/12/2703 If you use a bit of time, you should be able to find info and answers to your questions.

I will try to go through your questions quickly.

Fix and way so you know the orientation on the robot or use a calibration procedure
It is a personal choice where on the robot base_link is set, but some places are smarter than others. If you want to control a multi propelled drone, set in the center. For a front steered vehicle, general rotation point or center of mass might be a good choice. The trick is to know the static translations and rotation between IMU and base_link. The transform between base_link->IMU can be determined using either a fixed setup with known positions and orientations or a calibration procedure. We used a fixed setup based on a 3D printed sensor mount.
If the above information did not provide you with enough details, then have look at this VN-100 node: https://github.com/FroboLab/frobomind... You might choose another approach, but this should help you to move forward.

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Thanks for the answer. I will try the NED to ENU conversion. 1. Should there be any rotation between ENU and NED? On top of the republisher which converts the msg, should we add the transformation on the imu? 2. If i put the imu with label up at the baselink? Should I make a 180 roll for static_tf?

Marek ( 2018-06-14 04:03:12 -0500 )edit

I think you are at the point where you need to sit down and do some coding experiments to get the understanding you need :-) You should be able to create a simple setup and validate everything using RVIZ if you published the individual transforms.

mpc_agro ( 2018-06-15 03:39:53 -0500 )edit

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